This section provides background information related to the present disclosure which is not necessarily prior art.
In the prior art, the boundaries (also known as tracking boundaries)—often referred to the upstream boundary “UB” and the downstream boundary “DB'—that confine the robot's work area on a conveyor could only be defined by straight lines perpendicular to the flow direction of the parts on the conveyor surface. A robot can pick a part on the conveyor when it is in the picking area. The picking area is defined by the intersection of the circular work envelope of the robot and the boundaries UB and DB.
In prior art, the motion software controlling the motion of the robot allows the robot to pick or place as soon as a part is downstream of the upstream boundary UB. This is done even if the part is actually outside the work envelope. If the part is downstream of the upstream boundary, but outside the work envelope, the robot faults with a “Position not reachable” error causing downtime.
It is always desirable to maximize the picking area so that the robot has the ability to pick or place the maximum number of parts. However, if the distance between the perpendicular upstream and downstream boundaries is increased, then the probability of the “Position not reachable” error increases because the not reachable areas for parts increases.
To avoid the above described shortcomings, users have to perform complex custom programming to prevent the robot from picking in the not reachable areas and pick only in the picking area. This adds to robot software complexity and expense.
The restriction to use only straight perpendicular boundaries makes it impossible to maximize the picking area of the robot when there are objects or obstacles such as other machines or robots in the work envelope of the robot. The restriction to use only straight perpendicular boundaries does not allow the robot to not pick those parts that are on the edge of the work envelope in certain applications where it was desired for improving the picking rate.
While the prior art describes methods for avoiding collisions while operating robots, skew boundaries and circular boundaries for defining a picking area on a conveyor are not mentioned.